News

On Friday, 25 February, John Norton (University of Pittsburgh) will give a talk titled “Eternal Inflation: When Probabilities Fail” (abstract below).

The meeting will be online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

In eternally inflating cosmology, infinitely many pocket universes are seeded. Attempts to show that universes like our observable universe are probable amongst them have failed, since no unique probability measure is recoverable. This lack of definite probabilities is taken to reveal a complete predictive failure. Inductive inference over the pocket universes, it would seem, is impossible. I argue that this conclusion of impossibility mistakes the nature of the problem. It confuses the case in which no inductive inference is possible, with another in which a weaker inductive logic applies. The alternative, applicable inductive logic is determined by background conditions and is the same, non-probabilistic logic as applies to an infinite lottery. This inductive logic does not preclude all predictions, but does affirm that predictions useful to deciding for or against eternal inflation are precluded.

The Philosophy of Physics Group at the Warsaw University of Technology is happy to announce the program of the Warsaw Spacetime Colloquium for the upcoming term:

25 February (17:00-19:00 CET) – John Norton (University of Pittsburgh) – “Eternal Inflation: When Probabilities Fail.”

11 March (17:00-19:00 CET) – Claudio Calosi (University of Geneva) – “Out of All the Indifferences, Into One Thing: Wavefunction Monism.”

25 March (17:00-19:00 CET) – Samuel Fletcher (University of Minnesota, Twin Cities) – “What Gravitational Waves Really Teach Us about Energy.”

8 April (17:00-19:00 CEST) – Nick Huggett (University of Illinois at Chicago) – “Gravity Meets the Quantum in the Laboratory.”

22 April (17:00-19:00 CEST) – Juliusz Doboszewski (University of Bonn) – “No ‘No Go’ for LIGO Prediction.”

6 May (17:00-19:00 CEST) – Vincent Lam (University of Bern & Grenoble Alpes University) – TBA

20 May (17:00-19:00 CEST) – Carl Hoefer (ICREA and University of Barcelona) – TBA

3 June (17:00-19:00 CEST) – Michela Massimi (University of Edinburgh) – “Perspectival Modelling: Some Lessons from the History of Nuclear Models around 1930-50.”

All the meetings will be online on Zoom. If you have not registered yet, you can do so here.

You can address any query to Antonio Vassallo (antonio.vassallo@pw.edu.pl).

On Friday, 21 January, Richard Dawid (Stockholm University) will give a talk titled “Final but Incomplete – What String Theory May Suggest for 21st Century Physics” (abstract below).

The meeting will be online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

String theory has not come close to a complete formulation after half a century of intense research. On the other hand, a number of features of the theory suggest that the theory, once completed, may be a final theory. It is argued in this talk that those two conspicuous characteristics of string physics are related to each other. The property that links them together is the fact that string theory has no free parameters at a fundamental level. The talk will discuss what finality could mean under the given circumstances and will look at possible implications of this situation for the long term prospects of theory building in fundamental physics.

On Friday, 7 January, Elise Crull (City University of New York) will give a talk titled “You’re a Good Man, Harvey Brown: Quantum Rods & Clocks from Decoherence” (abstract below).

The meeting will be online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

Harvey Brown’s 2005 book Physical Relativity calls for the development of a constructive-theoretic (as opposed to principle-theoretic) interpretation of relativity: in short, for a quantum-dynamical description of rods and clocks. Significant issues, however, stand in the way of this project. For one, such an interpretation of GR will require carrying over the Strong Equivalence Principle from SR, and this is not trivial. For another, a quantum-dynamical GR is clearly in tension with the fact that the fields in Einstein’s field equations are classical.

On Friday, 17 December, Alastair Wilson (University of Birmingham) will give a talk titled “Fundamentality and Levels in Everettian Quantum Mechanics” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

Distinctions in fundamentality between different levels of description are central to the viability of contemporary decoherence-based Everettian quantum mechanics (EQM). This approach to quantum theory characteristically combines a determinate fundamental reality (one universal wavefunction) with an indeterminate emergent reality (multiple decoherent worlds). In this talk I explore how the Everettian appeal to fundamentality and emergence can be understood within existing metaphysical frameworks, identify grounding and concept fundamentality as promising theoretical tools, and use them to characterize a system of explanatory levels (with associated laws of nature) for EQM. This Everettian level structure encompasses and extends the ‘classical’ levels structure. The ‘classical’ levels of physics, chemistry, biology, etc. are recovered, but they are emergent in character and potentially variable across Everett worlds. EQM invokes an additional fundamental level, not present in the classical levels picture, and a novel potential role for self-location in interlevel metaphysics. When given a modal realist interpretation, EQM also makes trouble for supervenience-based approaches to levels.

On Friday, 3 December, David Albert (Columbia University) will give a talk titled “Physical Laws and Physical Things” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

I will consider several strategies for absorbing unwanted pieces of concrete physical ontology (for example: absolute/substantival Newtonian space, Maxwellian Electromagnetic fields, and especially and particularly quantum-mechanical wave-functions) into the metaphysical category of Laws. I will argue that these strategies work well for the case of Newtonian absolute space – but that they work poorly for the case of quantum-mechanical wave-functions.

On Friday, 19 November, Jeremy Butterfield & Henrique Gomes (University of Cambridge) will give a talk titled “Assessing the Hole Argument” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

We assess the hole argument in general relativity, and the related topics of the definitions of symmetries and determinism. We begin by rejecting the claim made in some recent literature that the sheer mathematics of the theory makes it mandatory to identify spacetime points “across possible worlds” by dragging along by the isomorphism. We agree that the mathematics is indifferent to the identity of points, and that in many contexts, drag-along is appropriate. But we argue that general relativity, and indeed other spacetime theories, use other means of “trans-world identification”, which we will call threading. Besides, they need to use threading, on pain of trivialising important constructions: even elementary ones like the Lie derivative.

On Friday, 5 November, Robert DiSalle (Western University) will give a talk titled “On the epistemological foundations of space-time geometry” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT
According to Einstein, what was central to the motivating arguments for the general theory of relativity included not only the familiar arguments about generalizing the relativity of motion, but also the more complicated argument about the empirical content of space-time geometry. On this matter, Einstein’s views, broadly speaking, reflected the influence and insight of Poincaré and Hilbert regarding the empirical interpretation of formal structures. More specifically, however, Einstein offered a reductive analysis of the empirical foundation of geometry, that is, the argument reducing geometrical measurements to observations of “point-coincidences.” This reductive argument in turn inspired logical empiricist conceptions of the empirical content of formal theories. This paper draws a sharp contrast between such conception and the way in which the theory actually determines its characteristic theoretical magnitudes, such as the curvature of space-time. It suggests that the reductive analysis ultimately obscures the empirical significance of general relativity as a novel theory of gravity and space-time, and the nature of the evidentiary basis for this dramatic conceptual shift. I outline an alternative account of how general relativity connects with spatial and temporal measurement, based in the history of the epistemology of geometry, by extending historical analyses of spatial measurement, and of the empirical character of non-Euclidean geometry, to the analysis of curved space-time. This account suggests, more generally, an account of scientific representation, and of the links between empirical descriptions and mathematical structures, that avoids the characteristic difficulties of standard recent approaches.

On Friday, 22 October, Gordon Belot (University of Michigan) will give a talk titled “The Mach-Einstein Principle of 1917-1918” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CEST). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT
In 1917 and 1918 Einstein was working on relativistic cosmology and on promoting and explaining general relativity in correspondence. During this period, the thesis that the spacetime metric should be determined by the distribution of matter played an important role in his thought. This talk is concerned with interpreting this thesis and with investigating its status in general relativity.

The paper “The Metaphysics of Decoherence” has just been published in Erkenntnis. Check out the publications section for the details.